Tetrafluoroethene (TFE) and hexafluoropropene (HFP) are widely used as monomers in the manufacture of plastic and elastomeric fluoropolymers. See, for example, J. Scheirs in Modern Fluoropolymers, Wiley, 1996. The worldwide consumption of TFE exceeds 105 tons/year. HFP is used as a comonomer to manufacture thermoplastic and elastomeric fluoropolymers and as starting material for making hexafluoropropene oxide (HFPO). The worldwide consumption of HFP is estimated to amount to 30,000 tons/year.
There are several known methods for manufacturing TFE and HFP. The most common method involves the thermal pyrolysis of CHCIF2 (R-22) at temperatures between 600° C. to 1,000° C. Such a process is described, for example, in U.S. Pat. No. 2,551,573. Since this process employs chlorinated raw materials it leads to partially fluorinated and chlorinated low molecular weight products which are difficult to remove from TFE and HFP. Thus providing high purity TFE involves expensive purification steps. Additionally, hydrochloric acid containing HF as impurity is formed as a by-product in large quantities. The hydrochloric acid either has to be discarded or purified at high costs for use in chemical applications.
Therefore, alternative processes have been developed, which do not employ chlorine-containing raw materials. These processes involve the thermal decomposition of fluorinated materials at high temperatures. For example, U.S. Pat. No. 5,611,896 describes a process where elemental fluorine is reacted with carbon to produce CF4, which is subsequently converted to TFE in a plasma torch in the presence of carbon. WO 2004/061160 A1 discloses a process for preparing TFE that comprises subjecting perfluorocarbon stream to a pyrolysis followed by quenching. The pyrolysis reaction is preferably carried out by adding carbon to the pyrolysis reaction.